Function _mm_floor_sd
#[target_feature(enable = "sse4.1")]
pub fn _mm_floor_sd(a: __m128d, b: __m128d) -> __m128dRound the lower double-precision (64-bit) floating-point element in b
down to an integer value, store the result as a double-precision
floating-point element in the lower element of the intrinsic result,
and copies the upper element from a to the upper element of the intrinsic
result.